Alo  o 

7  r—^Mwf 


Hawaii  Agricultural  Experiment  Station,-  >  :~ 

HONOLULU. 


U.S.  DEPOSITORY 


E.  V.  WILCOX,  Special  Agent  in  Charge 


PRESS   BULLETIN    MO.  25 


Carbon  Bisulphid  for  Killing  Weeds 

By    E.    V.    WILCOX  V%  •  X&\/ 

Special   Agent    in   Charge,    Hawaii   Agricultural   ExperinBent^ty*  • 

Station.  United  States  Department  of  Agriculture.         ***--!„'         ,*»'** 


In  the  perpetual  conflict  with  weeds  it  becomes  necessary 
to  make  use  of  every  weapon  which  shows  efficiency  in  destroy- 
ing them.  The  conditions  under  which  different  crops  are 
raised  indicate  different  methods  as  best  adapted  to  the  vari- 
ous conditions  of  each  case.  During  the  past  year  a  number 
of  experiments  have  been  made  with  carbon  bisulphid  in 
studying  its  effects  upon  various  herbaceous  and  shrubby 
weeds.  In  these  experiments,  the  amount  of  carbon  bisulphid 
used  varied  according  to  the  size  of  the  plant  to  be  destroyed. 
On  small-stemmed  plants  like  Croiolaria,  about  a  teaspoonful 
of  commercial  bisulphid  was  poured  down  the  stem,  from  about 
six  inches  above  the  ground.  The  amount  was  increased,  for 
larger  plants,  up  to  two  tablespoonfuls  for  guava  bushes  three 
or  four  inches  in  diameter.  The  plants  upon  which  most  of 
the  tests  were  made  were  lantana,  guava,  prickly-pear,  Stacluj- 
tarpheta  dicotoma  (one  of  the  plants  known  by  the  native  name 
Oi),  and  Crotalaria  incana.  In  all  cases,  as  just  indicated,  the 
carbon  bisulphid  was  poured  on  the  stem  at  a  point  about  six 
inches  above  the  surface  of  the  ground.  On  most  plants  carbon 
bisulphid  shows  no  effect  until  after  the  lapse  of  a  considerable 


period;  on  large  guavas  sometimes  two  or  three  months.  The 
effect  of  pouring  carbon  bisulphid  on  Crotalaria  was  to  cause 
the  death  of  the  plant,  root  and  branches,  within  four  to  ten 
days.  The  plants  remain  green,  and  apparently  normal,  until 
shortly  before  death,  when  the  leaves  suddenly  turn  yellow 
and  shrivel  up.  If  the  plants  are  then  carefully  removed  from 
the  soil  it  is  found  that  all  of  the  root-system  is  dead  and  the 
inner  tissues  of  the  roots  and  lower  part  of  the  stem  are  brown, 
or  otherwise  discolored. 

Lantana  bushes,  about  two  inches  in  diameter,  died  within 
seventeen  to  thirty-two  days  after  the  application  of  carbon 
bisulphid.  About  the  same  length  of  time  was  required  for 
the  destruction  of  Oi.  Young  prickly-pear  plants,  about  two 
feet  in  height,  were  found  to  be  exceedingly  sensitive  to  car- 
bon bisulphid.  In  some  cases,  the  plants  fell  over  on  the  ground 
within  twenty-four  hours  after  being  moistened  with  the 
liquid;   and  in  other  cases,  were  dead  within  two  days. 

With  guava,  the  effects  of  carbon  bisulphid  were  not  mani- 
fested for  a  much  longer  period,  in  some  cases  even  not  for 
two  or  three  months.  Finally,  however,  in  all  but  two  cases 
the  leaves  turned  yellow,  withered  up,  and  the  plant  died.  The 
dead  and  dying  trees  were  dug  out  and  the  roots  examined. 
In  every  case  the  roots  were  found  to  be  dead  to  the  tip  and 
their  whole  tissue  discolored.  In  one  case,  the  guava  tree  was 
over  six  inches  in  diameter  at  the  base. 

Apparently,  the  effect  of  carbon  bisulphid,  when  applied 
directly  to  the  stems  of  plants,  is  due  to  artificial  freezing.  As 
is  well  known,  the  liquid  volatilizes  almost  instantly  and  cools 
the  surface  so  suddenly  that  the  living  bark  is  destroyed.  It 
was  found  to  be  a  simple  matter  to  produce  ice  at  noon  on  hot 
days  on  the  surface  of  guavas  and  other  plants  by  slowly  drip- 
ping carbon  bisulphid  along  the  trunk.  The  death  of  large 
guavas  from  an  application  of  a  small  quantity  of  carbon 
bisulphid  to  the  base  of  the  trunk,  a  few  inches  above  the 
ground,  can  hardly  be  attributed  entirely  to  the  freezing  effect. 
It  seems  also  to  exercise  a  poisonous  action,  otherwise  it  would 
be  difficult  to  explain  the  complete  destruction  of  the  roots  to 


their  tips,  in  some  instances,  six  or  eight  feet  from  the  point 
where  the  carbon  bisulphid  was  applied.  It  was  found,  for 
example,  that  guava  bushes  would  live  for  five  to  seven  months 
after  the  bark  and  cambium  had  been  entirely  removed  from 
the  surface  of  the  ground  up  to  a  height  of  two  feet.  More- 
over, the  destruction  of  the  bark  at  the  base  of  the  trunk  by 
concentrated  sulphuric  acid  was  not  sufficient  to  cause  the 
death  of  the  guava  bush  for  about  six  months.  Apparently, 
therefore,  carbon  bisulphid  causes  the  death  of  plants  by  its 
freezing  effect  and  also  by  a  poisonous  action. 

The  use  of  carbon  bisulphid  for  destroying  underground 
insects  is  a  familiar  practice.  It  may  be  interesting,  therefore, 
to  inquire  what  effect,  if  any,  the  extensive  use  of  carbon  bisul- 
phid may  have  upon  the  soil  and  its  adaptability  to  cultivation. 
It  is  well  known,  for  example,  that  the  application  of  carbon 
bisulphid  to  the  soil  around  fruit  trees  and  other  plants  has 
no  injurious  effect  upon  the  plants ;  in  fact,  ^Hiltner  and 
Stormer  have  shown  that  carbon  bisulphid  reduces  denitrifica- 
tion  and  the  fixation  of  nitrogen.  Similarly,  ^Heinze  demon- 
strated that  carbon  bisulphid  promotes  the  activity  of  nitrogen- 
fixing  organisms.  In  experiments  carried  on  by  Nobbe,  the 
yield  of  peas,  and  various  other  crops,  was  increased  as  a  result 
of  the  application  of  carbon  bisulphid  and  the  plants  absorbed 
more  ash  and  nitrogen.  ^Henry  found  that  when  400  cc.  of 
carbon  bisulphid  per  square  meter  was  injected  into  the  soil 
about  locust  trees,  beneficial  effects  upon  the  growth  of  the 
trees  were  observed  for  several  years.  On  the  other  hand, 
heavy  fumigation  with  carbon  bisulphid  has  frequently  proved 
injurious  or  fatal  to  young  fruit  trees.  In  a  series  of  experi- 
ments by  ^Oberlin,  carried  on  for  eighteen  years,  in  treating 
grape  Phylloxera,  it  was  found  that  carbon  bisulphid  had  a 
remarkable  effect  in  increasing  the  yield  of  grapes.  "When 
other  crops  were  rotated  with  grapes,  for  example,  legumes, 


L.  Hiltner  and  K.  Stormer,  Arb.  K.  Gesundheitsamte,  Biol.  Abt.  3 
(1903)    pp.    443-545. 

B.  Heinze,  Centbl.  Bakt.,  etc.,  2  Abt.  16  (1906)  pp.  329-358. 
E.  Henry,  Bui.  Soc.  Sci.  Nancy,  3  Ser.  2  (1901)  pp.  27-33. 

C.  Oberlin,  Jour.  Agr.  Prat.  59  (1895)  pp.  459-464,  499-503,  535-540. 


UNIVERSITY  OF  FLORIDA 


3  1262  08929  9159 


sugar-beets,  and  cereals,  a  considerably  increased  yield  was 
also  noted  in  these  plants.  In  a  few  instances,  it  appeared  that 
soil  made  "sick"  by  continuous  culture  of  the  same  crop  was 
restored  to  productiveness  by  the  use  of  carbon  bisulphid. 

Apparently  the  only  previous  experiments  with  carbon 
bisulphid,  as  a  weed-destroyer,  were  carried  out  by  "Walker  in 
Arkansas  in  destroying  sassafras  sprouts,  and  by  the  writer, 
in  Maryland,  also  on  sassafras.  In  both  of  these  localities  the 
chemical  was  found  to  produce  the  death  of  the  plants  within 
one  month. 

In  using  carbon  bisulphid  it  should  always  be  remembered 
that  the  fumes,  if  inhaled  continuously,  may  produce  serious 
effects  upon  the  workmen,  and  also  that  the  material  is  highly 
inflammable  and  should  be  protected  from  accidental  flames. 
The  effects  of  the  fumes  upon  workmen  include  headache,  diz- 
ziness, hysterical  excitement,  and,  finally,  a  rather  serious 
weakness,  a  feeble  pulse  and  other  symptoms  of  prostration. 
If  it  is  used,  therefore,  in  the  eradication  of  weeds,  these  effects 
should  be  borne  in  mind  in  order  to  protect  the  workmen. 

It  is  obvious  that  carbon  bisulphid,  although  an  effective 
means  of  destroying  certain  weeds,  cannot  be  used  economi- 
cally in  all  localities.  There  are  many  steep  slopes  covered 
with  guavas,  in  which  it  would  be  a  very  difficult  matter  to 
operate  with  this  chemical.  It  is  always  necessary  for  the 
workmen  to  keep  to  the  windward,  in  order  to  avoid  the 
fumes,  and  in  some  localities  the  difficulty  of  transporting  con- 
tainers would  render  the  method  entirely  impracticable.  On 
the  other  hand,  the  use  of  carbon  bisulphid  in  the  destruction 
of  such  plants  as  the  guava  has  the  advantage  that  young 
sprouts  do  not  come  up  from  the  roots.  The  necessity  of  grub- 
bing out  all  of  the  roots  is  thus  obviated.  Under  such  circum- 
stances, it  would  merely  be  necessary  to  allow  the  guavas  to 
stand  until  they  are  dead,  after  which  the  trunk  and  large 
roots  would  be  removed,  as  is  necessary  in  any  case  in  clearing 
the  land. 


